Cygwin make always processing $(chrome_jar_file) target, after first successful build. So I never get up to date message and always see commands for $(chrome_jar_file) are executing.

However it happens only on Windows 7. On Windows XP once it built and intact, no more builds. I narrowed down the issue to one prerequisite - $(jar_target_dir).

Here is part of the code

# The location where the JAR file will be created.
jar_target_dir := $(build_dir)/chrome

# The main chrome JAR file.
chrome_jar_file := $(jar_target_dir)/$(extension_name).jar

# The root of the JAR sources.
jar_source_root := chrome

# The sources for the JAR file.
jar_sources := bla #... some files, doesn't matter

jar_sources_no_dir := $(subst $(jar_source_root)/,,$(jar_sources))

$(chrome_jar_file): $(jar_sources) $(jar_target_dir)
 @echo "Creating chrome JAR file."
 @cd $(jar_source_root); $(ZIP) ../$(chrome_jar_file) $(jar_sources_no_dir)
 @echo "Creating chrome JAR file. Done!"

$(jar_target_dir): $(build_dir)
 echo "Creating jar target dir..."
 if [ ! -x $(jar_target_dir) ]; \
  then \
    mkdir $(jar_target_dir); \
  fi

$(build_dir):
 @if [ ! -x $(build_dir) ]; \
  then \
    mkdir $(build_dir); \
  fi

so if I just remove $(jar_target_dir) from $(chrome_jar_file) rule, it works fine.